Forecast Forum - August  2003

The canonical correlation analysis (CCA) forecast of SST in the central Pacific (Barnett et al. 1988, Science, 241, 192-196; Barnston and Ropelewski 1992, J. Climate, 5, 1316-1345), is shown in Figs. F1 and F2. This forecast is produced routinely by the Prediction Branch of the Climate Prediction Center. The predictions from the National Centers for Environmental Prediction (NCEP) coupled ocean/atmosphere model (Ji et al. 1998, Mon. Wea. Rev, 126, 1022-1034) are presented in Figs. F3 and F4a, F4b.  Predictions from the Markov model (Xue, Y. et al. 2000: ENSO prediction with Markov model: The impact of sea level. J. Climate, 13, 849-871) are shown in Figs. F5 and F6.   Predictions from the latest version of the LDEO model (Chen, D. et al. 2000, Geophys. Res. Let., 27, 2585-2587) are shown in Figs. F7 and F8. Predictions using linear inverse modeling (Penland and Magorian 1993, J. Climate, 6, 1067-1076) are shown in Figs. F9 and F10. Predictions from the Scripps / Max Planck Institute (MPI) hybrid coupled model (Barnett et al. 1993, J. Climate, 6, 1545-1566) are shown in Fig. F11.   Predictions from the ENSO-CLIPER statistical model (Knaff, J. A. and C. W. Landsea 1997, Wea. Forecasting, 12, 633-652) are shown in Fig. F12.  Niño 3.4 predictions are summarized in F13, which is provided by the Forecasting and Prediction Research Group of the IRI.

The CPC and the contributors to the Forecast Forum caution potential users of this predictive information that they can expect only modest skill.

Outlook

Based on current conditions and recent observed trends, it is most likely that near average (ENSO-neutral) conditions will continue in the tropical Pacific through the Northern Hemisphere winter 2003-2004.

Discussion

Oceanic and atmospheric conditions in the tropical Pacific were near average (ENSO-neutral) during August 2003. Equatorial ocean surface temperatures greater than +0.5°C (~1°F) above average were found in the region between 150°E and 165°W while temperatures were below average between 90°W and the South American coast (Figs. T9, T18). During July and August very little net change was observed in the SST anomalies in the Niño regions (Table T2).

Positive equatorial upper-ocean temperature departures continued to weaken in the eastern Pacific during August 2003 while positive departures increased in magnitude in the central equatorial Pacific (Figs. T15, T17). Overall the basin-wide upper ocean heat content was slightly greater than average during the month (Fig. T17).

Some atmospheric indices, such as the Tahiti-Darwin SOI, and central Pacific low-level (850-hPa) zonal wind and OLR, have displayed considerable month-to-month variability and no consistent trend towards either La Niña or El Niño over the past few months (Table T1).

The latest statistical and coupled model forecasts indicate considerable uncertainty for the next several months (Figs. F1, F2, F3, F4a, F4b, F5, F6, F7, F8, F9, F10, F11, F12, F13).  However, a majority of the forecasts indicate near average (ENSO-neutral) conditions (Niño 3.4 SST anomalies between -0.5°C and +0.5°C) through the NH winter 2003-2004. This is consistent with current conditions and the lack of any consistent trends in the suite of oceanic and atmospheric indices.

Weekly updates of SST, 850-hPa wind, OLR and features of the equatorial subsurface thermal structure are available on the Climate Prediction Center homepage at: http://www.cpc.ncep.noaa.gov.